In a laser light source device, when a current is fed to a semiconductor laser array formed by arranging a plurality of semiconductor laser elements in an array, the semiconductor laser array serves as an oscillation source of laser light as well as a heat generation source generating a large heat. In the semiconductor laser array, an oscillation wavelength changes depending on a temperature, and at a high temperature a laser output decreases and then the reliability of the semiconductor laser array is reduced. It is thereby preferable to provide a cooling structure so as to hold a proper temperature in the semiconductor laser array. An example of a configuration of the laser light source device with the cooling structure is shown in a Patent Document 1.
In the Patent Document 1, a semiconductor laser array is joined by using a conductive paste such as solder onto a heat sink referred to a cooling body in which a flow channel for cooling water is included. A material for the heat sink needs to have excellent thermal conductivity in order to dissipate heat of the semiconductor laser array. Further, the material needs to have excellent insulating properties so as to prevent rapid progression of corrosion in the heat sink caused by electrolytic corrosion (electrical erosion in the flow channel for cooling water). As the material having both of these properties, ceramics have been used as the material for the heat sink. A metal plated layer is formed onto an entire upper surface of the heat sink with plating process to constitute a power feed path. With such a configuration, the power feed path and the cooling water flow channel are separated to prevent the electrolytic corrosion.